U.S. patent application number 14/110808 was filed with the patent office on 2014-01-23 for hydraulic working machine.
This patent application is currently assigned to HITACHI CONSTRUCTION MACHINERY CO., LTD.. The applicant listed for this patent is He Bao, Kazuo Fujishima, Masatoshi Hoshino, Seiji Ishida, Yusuke Kajita, Akira Nakayama, Takashi Okada, Mitsuo Sonoda, Junji Yamamoto, Shiro Yamaoka. Invention is credited to He Bao, Kazuo Fujishima, Masatoshi Hoshino, Seiji Ishida, Yusuke Kajita, Akira Nakayama, Takashi Okada, Mitsuo Sonoda, Junji Yamamoto, Shiro Yamaoka.
Application Number | 20140020375 14/110808 |
Document ID | / |
Family ID | 47217348 |
Filed Date | 2014-01-23 |
United States Patent
Application |
20140020375 |
Kind Code |
A1 |
Fujishima; Kazuo ; et
al. |
January 23, 2014 |
HYDRAULIC WORKING MACHINE
Abstract
A hydraulic working machine has an assist electric motor
connected to an engine and a hydraulic pump. The emissions of air
pollutants in the exhaust gas from the engine are minimized
regardless of fluctuations in the load torque of the hydraulic
pump. A specific revolution speed suitable for reducing the
emissions of air pollutants is stored, and an engine is controlled
using the specific revolution speed as a target revolution speed.
The absorption torque of a hydraulic pump is subjected to high-pass
filtering whereby a high-frequency component devoid of a trend
component is obtained. Target assist torque is computed from the
high-frequency component, and the assist electric motor is
subjected to power running/generation control accordingly. A
specific output torque range suitable for reducing the emissions of
air pollutants is stored, and the target assist torque is corrected
so that the trend component does not exceed the specific output
torque range.
Inventors: |
Fujishima; Kazuo;
(Tsuchiura-shi, JP) ; Kajita; Yusuke; (Ushiku-shi,
JP) ; Sonoda; Mitsuo; (Kasumigaura-shi, JP) ;
Hoshino; Masatoshi; (Tsuchiura-shi, JP) ; Nakayama;
Akira; (Tsuchiura-shi, JP) ; Yamamoto; Junji;
(Kasumigaura-shi, JP) ; Bao; He; (Ushiku-shi,
JP) ; Ishida; Seiji; (Hitachinaka-shi, JP) ;
Yamaoka; Shiro; (Hitachi-shi, JP) ; Okada;
Takashi; (Hitachinaka-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Fujishima; Kazuo
Kajita; Yusuke
Sonoda; Mitsuo
Hoshino; Masatoshi
Nakayama; Akira
Yamamoto; Junji
Bao; He
Ishida; Seiji
Yamaoka; Shiro
Okada; Takashi |
Tsuchiura-shi
Ushiku-shi
Kasumigaura-shi
Tsuchiura-shi
Tsuchiura-shi
Kasumigaura-shi
Ushiku-shi
Hitachinaka-shi
Hitachi-shi
Hitachinaka-shi |
|
JP
JP
JP
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
HITACHI CONSTRUCTION MACHINERY CO.,
LTD.
Tokyo
JP
|
Family ID: |
47217348 |
Appl. No.: |
14/110808 |
Filed: |
May 24, 2012 |
PCT Filed: |
May 24, 2012 |
PCT NO: |
PCT/JP2012/063370 |
371 Date: |
October 9, 2013 |
Current U.S.
Class: |
60/431 |
Current CPC
Class: |
F15B 2211/6316 20130101;
F02D 41/1406 20130101; B60W 20/00 20130101; Y02T 10/6217 20130101;
F02D 2250/36 20130101; B60Y 2200/412 20130101; F15B 2211/20546
20130101; B60W 20/15 20160101; F15B 2211/88 20130101; Y02T 10/6286
20130101; B60K 17/28 20130101; F02D 2250/18 20130101; B60W 10/06
20130101; F15B 21/14 20130101; B60W 2300/17 20130101; F15B 2211/633
20130101; F15B 2211/20515 20130101; B60W 30/1888 20130101; B60W
2710/0644 20130101; E02F 9/20 20130101; Y02T 10/62 20130101; E02F
9/2075 20130101; B60K 6/46 20130101; B60W 20/11 20160101; B60W
10/08 20130101; F02D 31/001 20130101; E02F 9/2025 20130101; F02D
2250/38 20130101; F15B 2211/20523 20130101; B60W 20/16 20160101;
E02F 9/2296 20130101 |
Class at
Publication: |
60/431 |
International
Class: |
E02F 9/20 20060101
E02F009/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2011 |
JP |
2011-117443 |
Claims
1. A hybrid-driven hydraulic working machine comprising: an engine
(7); a hydraulic pump (6) driven rotatably by said engine; an
assist electric motor (10) connected to said engine and said
hydraulic pump; a plurality of actuators (3a to 3c, 3e, 3f) driven
by hydraulic fluid delivered by said hydraulic pump; and a
plurality of operating devices (4a, 4b) each having an operating
member, said operating devices operating said actuators by
outputting an operation signal reflecting the operation of said
operating member; wherein said hybrid-driven hydraulic working
machine further includes: a storage device (11f; 11fA; 11fB) that
stores a specific revolution speed of said engine suitable for
reducing the emissions of air pollutants contained in exhaust gas
from said engine; an engine revolution speed setting device (11a;
11aB) that sets said specific revolution speed stored in said
storage device as a target revolution speed for said engine; an
engine revolution speed control device (21) that controls the
revolution speed of said engine based on said target revolution
speed for said engine, and an electric motor control device (11;
11A; 11B; 11C; 11D) that computes differential torque between the
absorption torque of said hydraulic pump and target output torque
of said engine and that subjects said assist electric motor to
power running control and generation control in accordance with the
differential torque.
2. The hybrid-driven hydraulic working machine according to claim
1, wherein said electric motor control device (11A; 11B; 11C; 11D)
includes a pump absorption torque acquiring device (11b; 11bC;
11bD) that acquires the absorption torque of said hydraulic pump
(6), and a filter device (11c1) that separates the absorption
torque of said hydraulic pump acquired by said pump absorption
torque acquiring device into a trend component as target torque for
said engine and other component, and wherein said electric motor
control device uses said other component separated by said filter
device as said differential torque, and subjects said assist
electric motor (10) to power running control and generation control
in such a manner that said trend component serves as the target
output torque for said engine.
3. The hybrid-driven hydraulic working machine according to claim
2, wherein said filter device (11c1) is a high-pass filter that
removes said trend component from the absorption torque of said
hydraulic pump (6) acquired by said pump absorption torque
acquiring device (11b; 11bC; 11bD).
4. The hybrid-driven hydraulic working machine according to claim
2, wherein said storage device (11fA; 11fB) stores a specific
revolution speed and a specific output torque range of said engine
suitable for reducing the emissions of air pollutants contained in
the exhaust gas from said engine (7); wherein said electric motor
control device (11A; 11B; 11C; 11D) further includes a torque
distribution correcting device (11e; 11eB) that corrects the target
torque for said assist electric motor (10) in such a manner that
the target output torque for said engine does not exceed said
specific output torque range stored in said storage device, and
wherein said electric motor control device subjects said assist
electric motor to power running control and generation control
based on the target torque for said assist electric motor corrected
by said torque distribution correcting device.
5. The hybrid-driven hydraulic working machine according to claim
1, wherein the exhaust gas from said engine (7) contains
particulate matter (PM) and nitrogen oxides, and said storage
device (11fA; 11fB) stores a specific revolution speed of said
engine, or a specific revolution speed and a specific output torque
range of said engine suitable for reducing one of a plurality of
factors including the emissions of particulate matter (PM), the
emissions of nitrogen oxides (NOx), the total emissions of
particulate matter (PM) and nitrogen oxides (NOx), a combination of
the emissions of particulate matter (PM) with fuel consumption, a
combination of the emissions of nitrogen oxides (NOx) with fuel
consumption, and a combination of the total emissions of
particulate matter (PM) and nitrogen oxides (NOx) with fuel
consumption.
6. The hybrid-driven hydraulic working machine according to claim
4, wherein the exhaust gas from said engine (7) contains
particulate matter (PM) and nitrogen oxides, and said storage
device (11fB) stores a plurality of combinations of said specific
revolution speed and said specific output torque range of said
engine suitable for reducing at least two of a plurality of factors
including the emissions of particulate matter (PM), the emissions
of nitrogen oxides (NOx), the total emissions of particulate matter
(PM) and nitrogen oxides (NOx), a combination of the emissions of
particulate matter (PM) with fuel consumption, a combination of the
emissions of nitrogen oxides (NOx) with fuel consumption, and a
combination of the total emissions of particulate matter (PM) and
nitrogen oxides (NOx) with fuel consumption; wherein said hydraulic
working machine further includes a switching device (22) that
selects for use one of the combinations of said specific revolution
speed and said specific output torque range of said engine; wherein
said engine revolution speed setting device (11aB) sets said
specific revolution speed of the combination selected by said
switching device as said target revolution speed for said engine,
and wherein said torque distribution correcting device (11eB)
corrects the target torque for said assist electric motor (10) in
such a manner that said specific output torque range of the
combination selected by said switching device is not exceeded.
7. The hybrid-driven hydraulic working machine according to claim
2, wherein said pump absorption torque acquiring device (11b)
includes: a torque detecting device (19) that detects the
absorption torque of said hydraulic pump (6); and a torque
computing device (11b) that computes the absorption torque of said
hydraulic pump based on detected values from said torque detecting
device.
8. The hybrid-driven hydraulic working machine according to claim
2, wherein said pump absorption torque acquiring device (11bC)
includes: a revolution detecting device (23) that detects the
actual revolution speed of said engine (7); and a torque computing
device (11bC) that estimates the absorption torque of said
hydraulic pump (6) based on the deviation between said actual
revolution speed detected by said revolution detecting device and
said target revolution speed.
9. The hybrid-driven hydraulic working machine according to claim
2, wherein said pump absorption torque acquiring device (11bD)
includes: an operation signal detecting device (26) that detects
the operation signal output from said plurality of operating
devices (4a, 4b), and a torque computing device (11bD) that
predicts the absorption torque of said hydraulic pump (6) based on
said operation signal detected by said operation signal detecting
device.
10. A hybrid-driven hydraulic working machine comprising: an engine
(7); a hydraulic pump (6) driven rotatably by said engine; an
assist electric motor (10) connected to said engine and said
hydraulic pump; a plurality of actuators (3a to 3c, 3e, 3f) driven
by hydraulic fluid delivered by said hydraulic pump, and a
plurality of operating devices (4a, 4b) each having an operating
member, said operating devices operating said actuators by
outputting an operation signal reflecting the operation of said
operating member; wherein said hybrid-driven hydraulic working
machine further includes: a storage device (11fE) that stores a
specific revolution speed and specific output torque of said engine
suitable for reducing the emissions of air pollutants contained in
exhaust gas from said engine; an engine revolution speed setting
device (11a) that sets said specific revolution speed stored in
said storage device as a target revolution speed for said engine;
an engine revolution speed control device (21) that controls the
revolution speed of said engine based on said target revolution
speed for said engine; and an electric motor control device (11E)
that computes the deviation between the absorption torque of said
hydraulic pump and said specific output torque stored in said
storage device and that subjects said assist electric motor to
power running control and generation control in accordance with the
deviation.
11. The hybrid-driven hydraulic working machine according to claim
10, wherein the exhaust gas from said engine (7) contains
particulate matter (PM) and nitrogen oxides, and a specific
revolution speed and specific output torque of said engine (7)
stored in said storage device (11fE) are suitable for reducing one
of a plurality of factors including the emissions of particulate
matter (PM), the emissions of nitrogen oxides (NOx), the total
emissions of particulate matter (PM) and nitrogen oxides (NOx), a
combination of the emissions of particulate matter (PM) with fuel
consumption, a combination of the emissions of nitrogen oxides
(NOx) with fuel consumption, and a combination of the total
emissions of particulate matter (PM) and nitrogen oxides (NOx) with
fuel consumption.
12. The hybrid-driven hydraulic working machine according to claim
4, wherein the exhaust gas from said engine (7) contains
particulate matter (PM) and nitrogen oxides, and said storage
device (11fA; 11fB) stores a specific revolution speed of said
engine, or a specific revolution speed and a specific output torque
range of said engine suitable for reducing one of a plurality of
factors including the emissions of particulate matter (PM), the
emissions of nitrogen oxides (NOx), the total emissions of
particulate matter (PM) and nitrogen oxides (NOx), a combination of
the emissions of particulate matter (PM) with fuel consumption, a
combination of the emissions of nitrogen oxides (NOx) with fuel
consumption, and a combination of the total emissions of
particulate matter (PM) and nitrogen oxides (NOx) with fuel
consumption.
Description
TECHNICAL FIELD
[0001] The present invention relates to hydraulic working machines
including hydraulic shovels, wheel loaders and others. More
particularly, the invention relates to a hybrid-driven hydraulic
working machine equipped with an assist electric motor driven by an
engine as well as by an electric storage device.
BACKGROUND ART
[0002] In recent years, the regulations on exhaust gases from
engines have become stricter. To deal with these regulations,
engine manufacturers and other makers have been trying in
particular to reduce particulate matter (PM) and nitrogen oxides
(NOx) contained in exhaust gases. A large number of advanced
combustion control techniques have been developed. On the other
hand, there have been developed techniques for performing the
processes of capturing and purifying particulate matter (PM) and
nitrogen oxides (NOx) by installing an exhaust gas after-treatment
device such as DPF (diesel particulate filter) and a urea SCR
system interposingly between the engine and the muffler. These
techniques are combined as needed with advanced combustion control
techniques to address the exhaust gas regulations that are getting
stricter all the time.
[0003] However, the above-mentioned exhaust gas after-treatment
devices such as the DPF (diesel particulate filter) and urea SCR
system were not originally attached to the engine system. Usually,
these exhaust gas after-treatment devices are complex in structure
and use expensive materials. For example, the catalyst used in the
PDF is platinum. Furthermore, the urea SCR system needs to be
provided with a tank for storing urea and a urea injecting device.
For these reasons, engine systems equipped with the exhaust gas
after-treatment device can be considerably more costly than
engine-only systems.
[0004] Meanwhile, in the field of hydraulic working machine such as
hydraulic shovels, there have been proposed and developed in recent
years hybrid-driven hydraulic working machines equipped with an
assist electric motor driven by an engine as well as by an electric
storage device such as batteries acting as a drive source.
[0005] For example, the construction machine (hydraulic working
machine) proposed in Patent Document 1 is equipped with an
engine-driven electric motor so that excess engine output is saved
as electric energy for energy conservation. When engine output is
insufficient, the saved electric energy is released to drive the
electric motor so as to maintain required pump absorption torque.
Patent Document 1 explains that this structure makes it possible to
adopt a small engine having rated output equivalent to the average
horsepower necessary for the construction machine to do its work
and that fuel efficiency can be improved and exhaust CO2 emissions
can be reduced accordingly.
[0006] The working machine proposed in FIG. 6 of Patent Document 2
is structured to generate hydraulic pressure with a hydraulic pump
driven by an engine and an electric motor. The rate of increase in
engine output is set to a predetermined value. An upper limit of
engine output obtained from the predetermined rate of increase is
compared with the demanded power acquired from the hydraulic output
demanded of the hydraulic pump. If the comparison shows that the
demanded power exceeds the upper limit of engine output, the
exceeding output is compensated for by electric motor output.
Patent Document 2 explains that even if hydraulic load is raised
suddenly, this structure performs control to prevent engine load
from getting abruptly raised thus keeping the operating conditions
of the engine within an appropriate range and that the drop of
combustion efficiency, generation of black exhaust, and engine
shutdown can be avoided accordingly.
PRIOR ART LITERATURE
Patent Document
[0007] Patent Document 1: Japanese Patent No. 4512283 [0008] Patent
Document 2: Japanese Patent No. 4633813
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0009] Unlike automobiles, hydraulic working machines such as
hydraulic shovels are subject to extreme fluctuations in engine
load. The load can fluctuate from 0 to 100 percent of the rated
engine torque instantaneously. It follows that no matter how
advanced engine combustion control is, there are limits to stably
reducing the emissions of particulate matter (PM) and nitrogen
oxides (NOx) by a predetermined amount under all working conditions
for hydraulic working machines. Usually, when there occur large
fluctuations in engine load and revolution speed, the emissions of
particulate matter (PM) and nitrogen oxides (NOx) tend to become
higher than in the steady state. Thus in order to reduce the
particulate matter (PM) and nitrogen oxides (NOx) contained in the
exhaust gases released into the atmosphere, it is necessary to
enlarge the capacity of the DPF and the volume of the tank in the
urea SCR system, or to install a urea injection control system
fine-tuned to address fuel injection status of the engine in the
urea SCR system. In any case, the costs involved will be high.
[0010] The hydraulic working machine described in Patent Document 1
and the one proposed in FIG. 6 of Patent Document 2 each subject
the electric motor to power running control to compensate for
insufficient engine output torque incurred when the torque demanded
of the hydraulic pump (pump absorption torque) exceeds engine
output torque, whereby engine load torque is prevented from getting
abruptly raised. However, there is no control associating the
target revolution speed and target output torque of the engine with
regions in which the emissions of air pollutants such as
particulate matter (PM) and nitrogen oxides (NOx) are to be
reduced. Thus, although the proposed machines are effective in
reducing fuel consumption, they fail to suitably reduce the
emissions of air pollutants such as particulate matter (PM) and
nitrogen oxides (NOx).
[0011] An object of the present invention is to provide a
hybrid-driven hydraulic working machine having an assist electric
motor connected to an engine and a hydraulic pump, the hydraulic
working machine being structured in such a manner that the
emissions of air pollutants in the exhaust gas from the engine are
minimized regardless of fluctuations in the load torque of the
hydraulic pump, that the rising cost of installing an exhaust gas
after-treatment device is lowered, and that the reliability of the
engine is enhanced.
[0012] (1) In achieving the above-stated object, the present
invention provides a hybrid-driven hydraulic working machine
including: an engine; a hydraulic pump driven rotatably by the
engine; an assist electric motor connected to the engine and the
hydraulic pump; a plurality of actuators driven by hydraulic fluid
delivered by the hydraulic pump; and a plurality of operating
devices each having an operating member, the operating devices
operating the actuators by outputting an operation signal
reflecting the operation of the operating member. The hybrid-driven
hydraulic working machine further includes: a storage device that
stores a specific revolution speed of the engine suitable for
reducing the emissions of air pollutants contained in exhaust gas
from the engine; an engine revolution speed setting device that
sets the specific revolution speed stored in the storage device as
a target revolution speed for the engine; an engine revolution
speed control device that controls the revolution speed of the
engine based on the target revolution speed for the engine; and an
electric motor control device that computes differential torque
between the absorption torque of the hydraulic pump and target
output torque of the engine and that subjects the assist electric
motor to power running control and generation control in accordance
with the differential torque.
[0013] As described above, a specific revolution speed of the
engine suitable for reducing the emissions of air pollutants
contained in the exhaust gas from the engine is set as a target
revolution speed for the engine, and the revolution speed of the
engine is controlled based on the target revolution speed. With the
engine revolution speed kept at a revolution speed for lowering the
emissions of air pollutants, it is possible to reduce the air
pollutant emissions. Moreover, while the engine revolution speed is
being controlled in this manner, the assist electric motor is
subjected to power running control and generation control in
accordance with the differential torque between the load torque
bearing on the engine and the target output torque for the engine.
This makes it possible to prevent abrupt fluctuations in the load
torque of the hydraulic pump from being transmitted unmitigated to
the engine when the load torque of the hydraulic pump (pump
absorption torque) exceeds engine output torque or when the load
torque of the hydraulic pump (pump absorption torque) becomes lower
than the engine output torque. The output torque of the engine is
controlled to stay equivalent to the target output torque for the
engine. As a result, the emissions of air pollutants contained in
the exhaust gas can be minimized.
[0014] Also, the engine revolution speed of the engine and the
assist electric motor are controlled to reduce the emissions of air
pollutants. This makes it possible to downsize or eliminate the
exhaust gas after-treatment device such as the DPF and urea SCR
system, whereby the rising cost of installing the exhaust gas
after-treatment device can be lowered.
[0015] Furthermore, when the assist electric motor is subjected to
power running control and generation control, the fluctuations in
the load bearing on the engine 7 are reduced. This offers the
additional benefit of prolonging the service life of the engine 7
and increasing the reliability of the engine.
[0016] (2) With regard to what is described in paragraph (1) above,
the electric motor control device may preferably include a pump
absorption torque acquiring device that acquires the absorption
torque of the hydraulic pump, and a filter device that separates
the absorption torque of the hydraulic pump acquired by the pump
absorption torque acquiring device into a trend component as target
torque for the engine and other component. The electric motor
control device may use the other component separated by the filter
device as the differential torque, and subject the assist electric
motor to power running control and generation control in such a
manner that the trend component serves as the target output torque
for the engine.
[0017] With this structure, as explained in paragraph (1) above,
the assist electric motor is subjected to power running/generation
control to keep the engine output torque equivalent to the target
output torque for the engine. This minimizes the emissions of air
pollutants contained in the exhaust gas, lowers the rising cost of
installing the exhaust gas after-treatment device, and improves the
reliability of the engine.
[0018] (3) With regard to what is described in paragraph (2) above,
the filter device may preferably be a high-pass filter that removes
the trend component from the absorption torque of the hydraulic
pump acquired by the pump absorption torque acquiring device.
[0019] With this structure, the differential torque is obtained
from the absorption torque of the hydraulic pump acquired by the
pump absorption torque acquiring device. As explained in paragraph
(1) above, the assist electric motor is subjected to power
running/generation control to keep the engine output torque
equivalent to the target output torque for the engine. This
minimizes the emissions of air pollutants contained in the exhaust
gas, lowers the rising cost of installing the exhaust gas
after-treatment device, and improves the reliability of the
engine.
[0020] (4) Also with regard to what is described in paragraph (2)
above, the storage device may preferably store a specific
revolution speed and a specific output torque range of the engine
suitable for reducing the emissions of air pollutants contained in
the exhaust gas from the engine; the electric motor control device
may further include a torque distribution correcting device that
corrects the target torque for the electric motor in such a manner
that the target output torque for the engine does not exceed the
specific output torque range stored in the storage device; and the
electric motor control device may subject the assist electric motor
to power running control and generation control based on the target
torque for the electric motor corrected by the torque distribution
correcting device.
[0021] With this structure, as described in paragraph (1) above,
control of the engine revolution speed and power running/generation
control of the assist electric motor can suppress the emissions of
air pollutants. Furthermore, the emissions of air pollutants can be
lowered by performing control in such a manner that the output
torque of the engine is kept within a specific output torque range
suitable for reducing the emissions of air pollutants.
[0022] (5) With regard to what is described in paragraph (1) or (4)
above, the exhaust gas from the engine contains particulate matter
(PM) and nitrogen oxides, and the storage device may preferably
store a specific revolution speed of the engine, or a specific
revolution speed and a specific output torque range of the engine
suitable for reducing one of a plurality of factors including the
emissions of particulate matter (PM), nitrogen oxides (NOx), the
total emissions of particulate matter (PM) and nitrogen oxides
(NOx), a combination of the emissions of particulate matter (PM)
with fuel consumption, a combination of the emissions of nitrogen
oxides (NOx) with fuel consumption, and a combination of the total
emissions of particulate matter (PM) and nitrogen oxides (NOx) with
fuel consumption.
[0023] With this structure, in paragraphs (1) and (4), power
running/generation control of the assist electric motor can reduce
the emissions of air pollutants. Furthermore, performing control to
keep the revolution speed and output torque of the engine within a
specific rotating speed and a specific output torque range can
lower one of a plurality of factors including the emissions of
particulate matter (PM), nitrogen oxides (NOx), the total emissions
of particulate matter (PM) and nitrogen oxides (NOx), a combination
of the emissions of particulate matter (PM) with fuel consumption,
a combination of the emissions of nitrogen oxides (NOx) with fuel
consumption, and a combination of the total emissions of
particulate matter (PM) and nitrogen oxides (NOx) with fuel
consumption.
[0024] (6) Also with regard to what is described in paragraph (4)
above, the exhaust gas from the engine contains particulate matter
(PM) and nitrogen oxides, and the storage device may preferably
store a plurality of combinations of the specific revolution speed
and the specific output torque range of the engine suitable for
reducing at least two of a plurality of factors including the
emissions of particulate matter (PM), nitrogen oxides (NOx), the
total emissions of particulate matter (PM) and nitrogen oxides
(NOx), a combination of the emissions of particulate matter (PM)
with fuel consumption, a combination of the emissions of nitrogen
oxides (NOx) with fuel consumption, and a combination of the total
emissions of particulate matter (PM) and nitrogen oxides (NOx) with
fuel consumption; and the hydraulic working machine may further
include a switching device that selects for use one of the
combinations of the specific revolution speed and the specific
output torque range of the engine.
[0025] The engine revolution speed setting device may set the
specific revolution speed of the combination selected by the
switching device as the target revolution speed for the engine, and
the torque distribution correcting device may correct the target
torque for the electric motor in such a manner that the specific
output torque range of the combination selected by the switching
device is not exceeded.
[0026] With this structure, as explained in paragraph (4) above,
when control is performed to reduce the emissions of air
pollutants, it is possible to select the combination of a specific
revolution speed and a specific output torque range of the engine
suitable for lowering the factors that are optimal for addressing
the regulations on the work environment and working area. Thus it
is possible to perform engine control and electric motor control
optimally fit for the regulations on the work environment and
working area.
[0027] (7) Also with regard to what is described in paragraph (2)
above, the pump absorption torque acquiring device may preferably
include a torque detecting device that detects the absorption
torque of the hydraulic pump, and a torque computing device that
computes the absorption torque of the hydraulic pump based on
detected values from the torque detecting device.
[0028] With this structure, it is possible to acquire accurate pump
absorption torque and thereby perform control with precision.
[0029] (8) Also with regard to what is described in paragraph (2)
above, the pump absorption torque acquiring device may preferably
include a revolution detecting device that detects the actual
revolution speed of the engine, and a torque computing device that
estimates the absorption torque of the hydraulic pump based on the
deviation between the actual revolution speed detected by the
revolution detecting device and the target revolution speed.
[0030] With this structure, a highly versatile revolution speed
detecting device may be used to acquire pump absorption torque.
This makes it possible to configure the system inexpensively.
[0031] (9) Also with regard to what is described in paragraph (2)
above, the pump absorption torque acquiring device may preferably
include an operation signal detecting device that detects the
operation signal output from the plurality of operating devices,
and a torque computing device that predicts the absorption torque
of the hydraulic pump based on the operation signal detected by the
operation signal detecting device.
[0032] With this structure, a highly versatile operation signal
detecting device may be used to acquire pump absorption torque.
This makes it possible to configure the system inexpensively.
[0033] (10) In achieving the above-stated object, the present
invention further provides a hybrid-driven hydraulic working
machine including: an engine; a hydraulic pump driven rotatably by
the engine; an assist electric motor connected to the engine and
the hydraulic pump; a plurality of actuators driven by hydraulic
fluid delivered by the hydraulic pump; and a plurality of operating
devices each having an operating member, the operating devices
operating the actuators by outputting an operation signal
reflecting the operation of the operating member. The hybrid-driven
hydraulic working machine further includes: a storage device that
stores a specific revolution speed and specific output torque of
the engine suitable for reducing the emissions of air pollutants
contained in exhaust gas from the engine; an engine revolution
speed setting device that sets the specific revolution speed stored
in the storage device as a target revolution speed for the engine;
an engine revolution speed control device that controls the
revolution speed of the engine based on the target revolution speed
for the engine; and an electric motor control device that computes
the deviation between the absorption torque of the hydraulic pump
and the specific output torque stored in the storage device and
that subjects the assist electric motor to power running control
and generation control in accordance with the deviation.
[0034] As described above, a specific output torque suitable for
reducing the emissions of air pollutants is set as target output
torque for the engine in order to control the engine revolution
speed. At the same time, the assist electric motor is subjected to
power running control and generation control in accordance with the
deviation between the absorption torque of the hydraulic pump and
specific output torque suitable for reducing the emissions of air
pollutants. This allows engine output torque to be controlled while
the specific output torque suitable for reducing the emissions of
air pollutants is set as the target output torque. That in turn
minimizes the emissions of air pollutants contained in the exhaust
gas, lowers the rising cost of installing the exhaust gas
after-treatment device, and increases the reliability of the
engine.
[0035] (11) With regard to what is described in paragraph (10)
above, the exhaust gas from the engine contains particulate matter
(PM) and nitrogen oxides, and a specific revolution speed and
specific output torque of the engine stored in the storage device
may preferably be those suitable for reducing one of a plurality of
factors including the emissions of particulate matter (PM),
nitrogen oxides (NOx), the total emissions of particulate matter
(PM) and nitrogen oxides (NOx), a combination of the emissions of
particulate matter (PM) with fuel consumption, a combination of the
emissions of nitrogen oxides (NOx) with fuel consumption, and a
combination of the total emissions of particulate matter (PM) and
nitrogen oxides (NOx) with fuel consumption.
[0036] With this structure, control of the engine revolution speed
and control of the engine output torque explained in paragraph (10)
above may reduce one of a plurality of factors including the
emissions of particulate matter (PM), nitrogen oxides (NOx), the
total emissions of particulate matter (PM) and nitrogen oxides
(NOx), a combination of the emissions of particulate matter (PM)
with fuel consumption, a combination of the emissions of nitrogen
oxides (NOx) with fuel consumption, and a combination of the total
emissions of particulate matter (PM) and nitrogen oxides (NOx) with
fuel consumption.
Effect of the Invention
[0037] According to the present invention, it is possible to
minimize the emissions of air pollutants contained in the exhaust
gas.
[0038] Also, with the emissions of air pollutants thus reduced, it
is possible to downsize or eliminate the exhaust gas
after-treatment device such as the DPF and urea SCR system, whereby
the rising cost of installing the exhaust gas after-treatment
device can be lowered.
[0039] Furthermore, subjecting the assist electric motor to power
running control and generation control reduces the fluctuations in
the load bearing on the engine, so that the service life of the
engine may be prolonged and the reliability of the engine may be
improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is an external view of a hydraulic shovel (hydraulic
working machine) as a first embodiment of the present
invention.
[0041] FIG. 2 is a block diagram of an actuator drive control
system mounted on the hydraulic shovel.
[0042] FIG. 3 is an illustration showing typical fluctuations in
the load torque bearing on a hydraulic pump of an ordinary actuator
drive control system which is devoid of an assist electric motor
and of which the hydraulic pump is driven only by an engine.
[0043] FIG. 4 is an explanatory view showing the idea of
suppressing large fluctuations in pump absorption torque using an
assist electric motor.
[0044] FIG. 5 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by a vehicle body controller.
[0045] FIG. 6 is an illustration showing the concept of processing
by a high-pass filter processing unit.
[0046] FIG. 7 is an illustration showing the concept of processing
by a target assist torque conversion processing unit.
[0047] FIG. 8 is an illustration showing the concept of processing
by an assist electric motor power running/generation computing
unit.
[0048] FIG. 9 is an illustration showing the whole concept of
processing by a target assist torque computing unit and by the
assist electric motor power running/generation computing unit.
[0049] FIG. 10 is a diagrammatic view showing line maps of the
emissions of particulate matter (PM) and those of nitrogen oxides
(NOx) contained in the exhaust gas from an engine, each of the maps
representing the correlations between the revolution speed and
output torque of the engine.
[0050] FIG. 11 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by a vehicle body controller as a second
embodiment of the present invention.
[0051] FIG. 12 is an illustration showing the concept of processing
by an engine output torque computing unit.
[0052] FIG. 13 is an illustration showing the concept of processing
by a target assist torque correcting unit.
[0053] FIG. 14 is an illustration showing the concept of processing
by another assist electric motor power running/generation computing
unit.
[0054] FIG. 15 is a diagrammatic view showing line maps of the
emissions of particulate matter (PM) contained in the exhaust gas
from the engine and the fuel consumption of the engine, each of the
maps representing the correlations between the revolution speed and
output torque of the engine.
[0055] FIG. 16 is a diagrammatic view showing line maps of the
emissions of nitrogen oxides (NOx) contained in the exhaust gas
from the engine and the fuel consumption of the engine, each of the
maps representing the correlations between the revolution speed and
output torque of the engine.
[0056] FIG. 17 is a diagrammatic view showing line maps of the
emissions of particulate matter (PM) contained in the exhaust gas
from the engine, the emissions of nitrogen oxides (NOx) in the
exhaust gas from the engine, and the fuel consumption of the
engine, each of the maps representing the correlations between the
revolution speed and output torque of the engine.
[0057] FIG. 18 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by a vehicle body controller as a third
embodiment of the present invention.
[0058] FIG. 19 is a block diagram of an actuator drive control
system mounted on a hydraulic shovel as a fourth embodiment of the
present invention.
[0059] FIG. 20 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by another vehicle body controller.
[0060] FIG. 21 is an illustration showing the concept of processing
by an engine revolution deviation computing unit and a pump
absorption torque estimating unit.
[0061] FIG. 22 is a block diagram of an actuator drive control
system as a fifth embodiment of the present invention.
[0062] FIG. 23 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by another vehicle body controller.
[0063] FIG. 24 is an illustration showing the concept of processing
by a proportional differential processing unit and a gain
processing unit.
[0064] FIG. 25 is a block diagram of an actuator drive control
system mounted on a hydraulic shovel as a sixth embodiment of the
present invention.
[0065] FIG. 26 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by another vehicle body controller.
[0066] FIG. 27 is a diagrammatic view showing a line map of the
emissions of particulate matter (PM) contained in the exhaust gas
from the engine, the map representing the correlations between the
revolution speed and output torque of the engine.
MODE FOR CARRYING OUT THE INVENTION
[0067] Some embodiments of the present invention are explained
below in reference to the accompanying drawings.
First Embodiment
[0068] FIG. 1 is an external view of a hydraulic shovel (hydraulic
working machine) as the first embodiment of the present
invention.
[0069] The hydraulic shovel is made up of a multi-jointed front
device 1A composed of a boom 1a, arm 1b and a bucket 1c each
rotating in the vertical direction, and a vehicle body 1B formed by
an upper swing structure 1d and a lower track structure 1e, the
base end of the boom 1a of the front device 1A being supported in a
vertically rotatable manner by the front section of the upper swing
structure 1d. The boom 1a, arm 1b, bucket 1c, upper swing structure
1d, and lower track structure 1e are driven, respectively, by a
boom cylinder 3a, an arm cylinder 3b, a bucket cylinder 3c, a swing
motor 16 (see FIG. 2), and left-hand and right-hand track motors 3e
and 3f. The movements of the boom 1a, arm 1b, bucket 1c, and upper
swing structure 1d are designated using hydraulic operation signals
(control pilot pressures) from control lever devices 4a and 4b (see
FIG. 2). The movements of the lower track structure 1e are
designated using hydraulic operation signals (control pilot
pressures) from a control pedal devices (not shown) for
tracking.
[0070] FIG. 2 is a block diagram of an actuator drive control
system mounted on the hydraulic shovel shown in FIG. 1.
[0071] In FIG. 2, the actuator drive control system of this
invention includes the control lever devices 4a and 4b, control
pedal devices (not shown) for tracking, spool type directional
control valves 5a to 5c, 5e and 5f; a main hydraulic pump 6, an
engine 7, a main relief valve 8, a tank 9, and a shuttle valve
block 25.
[0072] The control lever devices 4a and 4b and the control pedal
devices reduce the primary pressure generated by delivered fluid
from a pilot pump (not shown) into a secondary pressure to generate
a control pilot pressure (hydraulic operation signal) in accordance
with the opening degrees of pressure reducing valves (remote
control valves) attached to the control lever devices 4a and 4b and
control pedal devices. The control pilot pressure is then led to
pressure receiving units of the directional control valves 5a to
5c, 5e and 5f, whereby the directional control valves 5a to 5c, 5e
and 5f are switched from their neutral positions illustrated. The
directional control valves 5a to 5c, 5e and 5f may be, for example,
open center type spool valves disposed in a center bypass line.
Switched by the control pilot pressure, the directional control
valves control the flow (direction and flow rate) of hydraulic
fluid delivered by the hydraulic pump 6, whereby the drive of
hydraulic actuators 3a to 3c, 3e and 3f is controlled. The
hydraulic pump 6 is rotatably driven by the engine 7. In case of an
excessive rise in the pressure inside hydraulic piping into which
the delivered fluid from the hydraulic pump 6 is introduced, the
relief valve 8 relieves the hydraulic fluid into the tank 9 to
prevent an inordinate rise in the pressure within the hydraulic
piping.
[0073] The shuttle valve block 25 selectively outputs the hydraulic
operation signal of the highest pressure from among the hydraulic
operation signals (control pilot pressures) generated by the
control lever devices 4a and 4b other than those for designating
swing operations, and from among the hydraulic operation signals
generated by the control pedal devices (not shown).
[0074] The hydraulic pump 6 is a variable displacement type pump
that has a regulator 6a operating on a positive control method. The
hydraulic operation signal output by the shuttle valve block 25 is
led to the regulator 6a. As is well known, the regulator 6a of the
positive control method increases a swash plate tilting angle
(displacement) of the hydraulic pump 6 when the hydraulic operation
signal is raised by an increased operation amount (demanded flow
rate) of the control levers and pedals (operating members) of the
control lever devices 4a and 4b and control pedal devices, whereby
the delivery flow rate of the hydraulic pump 6 is increased.
[0075] Alternatively, the regulator 6a of the hydraulic pump 6 may
be one that operates on a negative control method whereby the
tilting angle (displacement) of the hydraulic pump 6 is increased
as the signal pressure input to the regulator 6a is lowered. In
this case, a throttle is mounted on the most downstream portion of
the center bypass line that leads to the tank 9 by way of the
directional control valves 5a to 5c, 5e and 5f. The pressure at the
inflow side of this throttle is taken as a signal pressure that is
led to the regulator 6a. In the case where the throttle is mounted
on the most downstream portion of the center bypass line, the
pressure at the inflow side of the throttle drops when the flow
rate through the center bypass throttle of the directional control
valves 5a to 5c, 5e and 5f is lowered in response to an increased
operation amount (demanded flow rate) of the control levers and
pedals (operating members) of the control lever devices 4a and 4b
and control pedal devices. Thus when the pressure at the inflow
side of the throttle is input to the regulator 6a as a signal
pressure, with the tilting angle (displacement) of the hydraulic
pump 6 increased in response to a drop in the signal pressure, it
is possible to raise the delivery flow rate of the hydraulic pump 6
in keeping with the increased operation amount of the operating
members.
[0076] Alternatively, there may be adopted a load sensing control
method whereby, with the directional control valves 5a to 5c, 5e
and 5f composed of a closed type spool valve each, the delivery
pressure of the hydraulic pump 6 is controlled to be higher than a
maximum load pressure by a predetermined pressure level.
[0077] Also, the regulator 6a is provided with a known torque
limitation control function for keeping the absorption torque of
the hydraulic pump 6 from exceeding predetermined maximum torque by
lowering the tilting angle (displacement) of the hydraulic pump 6
as the delivery pressure of the hydraulic pump 6 is increased.
[0078] The actuator drive control system of this embodiment further
includes an assist electric motor 10, a vehicle body controller 11,
inverters 12 and 13, a chopper 14, a battery 15, pressure sensors
17 and 18, a torque sensor 19, an engine control dial 20, a
revolution sensor 23 for detecting the revolution speed of the
engine 7, and an engine controller 21.
[0079] The assist electric motor 10 is connected between the
hydraulic pump 6 and the engine 7. The assist electric motor 10 has
the function of an electric generator that converts the power of
the engine 7 into electric energy (electric power) to be output to
the inverter 12, as well as the function of an electric motor that
assists in driving the hydraulic pump 6 when driven by the electric
energy (electric power) fed from the inverter 12.
[0080] When the assist electric motor 10 functions as an electric
generator, the inverter 12 converts the AC power generated by the
motor 10 into DC power to be output. When the assist electric motor
10 functions as an electric motor, the inverter 12 converts the DC
power from the battery 15 into AC power to be supplied to the
assist electric motor 10.
[0081] The inverter 13 converts the DC power generated by the
assist electric motor 10 and output by the inverter 12 into AC
power to be supplied to the swing motor 16. While at swing braking,
the inverter 13 converts the AC power regenerated by the swing
motor 16 acting as an electric generator into DC power to be
output.
[0082] The battery 15 has its voltage regulated through the chopper
14 and supplies electric power to the inverters 12 and 13. The
battery 15 also stores the electric energy generated by the assist
electric motor 10 as well as electric energy coming from the swing
motor 16.
[0083] The engine control dial 20 is operated by an operator to
give the command of a basic revolution speed of the engine 7
reflecting the operator's intentions. The vehicle body controller
11 receives the command signal from the engine control dial 20,
computes a target revolution speed based on the input command
signal, and outputs the computed target revolution speed to the
engine controller 21. The engine controller 21 computes the
deviation between the target revolution speed from the vehicle body
controller 11 and the actual revolution speed of the engine 7
detected by the revolution sensor 23, computes a target fuel
injection amount based on the computed revolution speed deviation,
and outputs a control signal reflecting the computed amount to an
electronic governor 7a attached to the engine 7. The electronic
governor 7a acting on that control signal causes the fuel
equivalent to the target fuel injection amount to be injected into
the engine 7. This allows the engine 7 to be controlled to maintain
its target revolution speed.
[0084] The vehicle body controller 11 has a control computing
circuit that performs the following controls regarding the assist
electric motor 10 and swing motor 16.
(1) Drive Control of the Swing Motor 16
[0085] The pressure sensors 17 and 18 are connected to a pilot
hydraulic line that conducts hydraulic operation signals for
designating swing operations in the right and left direction from
among the hydraulic operation signals generated by the control
lever device 4b, and detects the swing-designating hydraulic
operation signals. The vehicle body controller 11 receives
detection signals (electric signals) from the pressure sensors 17
and 18 and performs drive control of the swing motor 16 in
accordance with the detected hydraulic operation signals.
Specifically, upon detecting a hydraulic operation signal
designating a swing operation in the left direction, the vehicle
body controller 11 performs generation control whereby the inverter
12 is controlled based on the detected hydraulic operation signal
to let the assist electric motor 10 serve as an electric generator,
and carries out power running control whereby the inverter 13 is
controlled to drive the swing motor 16 thereby swinging the upper
swing structure 1d in the left direction at a speed corresponding
to the hydraulic operation signal. Upon detecting a hydraulic
operation signal designating a swing operation in the right
direction, the vehicle body controller 11 performs generation
control whereby the inverter 12 is controlled based on the detected
hydraulic operation signal to let the assist electric motor 10
serve as an electric generator, and carries out power running
control whereby the inverter 13 is controlled to drive the swing
motor 16 thereby swinging the upper swing structure 1d in the right
direction at a speed corresponding to the hydraulic operation
signal.
(2) Electric Storage Control of Recovered Electric Power
[0086] At swing braking, the vehicle body controller 11 performs
generation control whereby the inverter 13 is controlled to let the
swing motor 16 serve as an electric generator, thereby recovering
electric energy from the swing motor 16 and storing the recovered
electric energy into the battery 15.
(3) Control 1 of the Assist Electric Motor 10 (Electric Storage
Management and Control of the Battery 15)
[0087] When the hydraulic load on the hydraulic pump 6 (pump
absorption torque) is light and when the level of stored
electricity in the battery 15 is low, the vehicle body controller
11 performs generation control whereby the inverter 12 is
controlled to allow the assist electric motor 10 to serve as an
electric generator generating excess electric power and to store
the generated excess electric power into the battery 15.
Conversely, when the hydraulic load on the hydraulic pump 6 (pump
absorption torque) is heavy and when the level of stored
electricity in the battery 15 is higher than a predetermined level,
the vehicle body controller 11 performs power running control
whereby the inverter 12 is controlled to allow the assist electric
motor 10 to be supplied with electric power from the battery 15 and
to allow the assist electric motor 10 serve as an electric motor
assisting in driving the hydraulic pump 6. It should be noted that
when the hydraulic load on the hydraulic pump 6 (pump absorption
torque) is light and when the level of stored electricity in the
battery 15 is low, control 1 is given priority.
(4) Control 2 of the Assist Electric Motor 10 (Torque Fluctuation
Suppression Control)
[0088] The torque sensor 19 detects the load torque of the
hydraulic pump 6 (pump absorption torque) that fluctuates in
keeping with the fluctuations in the load bearing on the hydraulic
actuators 3a to 3c, 3e and 3f of the hydraulic shovel. The vehicle
body controller 11 receives a detection signal (electric signal)
from the torque sensor 19 and, based on the detected load torque of
the hydraulic pump 6, selectively performs either power running
control allowing the assist electric motor 10 to serve as an
electric motor, or generation control allowing the assist electric
motor 10 to serve as an electric generator, thereby suppressing the
output torque of the engine 7. This reduces the emissions of air
pollutants (particulate matter (PM) and nitrogen oxides (NOx))
contained in the exhaust gas from the engine 7.
[0089] The detailed function of torque fluctuation suppression
control performed by the vehicle body controller 11 is explained
below.
[0090] FIG. 3 is an illustration showing typical fluctuations in
the load torque bearing on the hydraulic pump 6 of an ordinary
actuator drive control system which is devoid of the assist
electric motor 10 and of which the hydraulic pump 6 is driven only
by the engine 7. FIG. 4 is an explanatory view showing the idea of
suppressing large fluctuations in pump absorption torque using the
assist electric motor 10. In this ordinary actuator drive control
system allowing the hydraulic pump 6 to be driven only by the
engine 7, the rotating bodies consisting of the hydraulic pump 6
and engine 7 share a rotary shaft. The fluctuations in the load
torque bearing on the hydraulic pump 6 shown in FIG. 3 are
equivalent to the fluctuations in the load torque of the engine
7.
[0091] Unlike automobiles or the like, construction working
machines such as hydraulic shovels are subject to very large
fluctuations in the load torque (pump absorption torque) of the
hydraulic pump, the fluctuations stemming from those in the load
bearing on actuators as shown in FIG. 3. As a result, the
fluctuations in the load on the engine are also extremely large.
For example, the load torque of the engine 7 can vary from about 0
to 100 percent instantaneously as illustrated in FIG. 3. According
to its basic characteristics, the engine is subject to large
fluctuations in engine revolution speed if there occur significant
fluctuations in load torque while the engine is running under the
conditions of a constant revolution speed/constant torque. This can
entail a tendency toward growing emissions of particulate matter
(PM) and nitrogen oxides (NOx) which are air pollutants contained
in the exhaust gas.
[0092] Thus with this embodiment, while the revolution speed of the
engine 7 is being controlled to stay at a predetermined revolution
speed, the assist electric motor 10 connected interposingly between
the hydraulic pump 6 and the engine 7 is controlled to ease the
large load torque fluctuations bearing on the hydraulic pump 6
(fluctuations in pump absorption torque) as shown in the bottom
right part of FIG. 4, whereby the emissions of PM and NOx stemming
from the fluctuations in revolution speed/torque are suppressed.
That is, while the engine 7 is being controlled to maintain its
predetermined engine revolution speed, the load torque of the
hydraulic pump 6 is separated into a trend component (low-frequency
component) and the remaining high-frequency component (transient
component) thereof. Power running/generation control commands are
then issued to the assist electric motor 10 in such a manner that
the high-frequency component is removed. This causes the output
torque of the engine 7 to remain within a predetermined range
(i.e., target output torque for the engine 7 corresponding to the
trend component of the load torque (pump absorption torque) of the
hydraulic pump 6), whereby the emissions of particulate matter (PM)
and nitrogen oxides (NOx) as air pollutants in the exhaust gas can
be minimized.
[0093] FIG. 5 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by the vehicle body controller 11.
[0094] The vehicle body controller 11 includes the functions
composed of a target revolution speed computing unit 11a, a pump
absorption torque computing unit 11b, a target assist torque
computing unit 11c, and an assist electric motor power
running/generation computing unit 11d; and a storage device
11f.
[0095] The storage device 11f stores an engine revolution speed Nea
(see FIG. 10) as a specific engine revolution speed suitable for
reducing the emissions of particulate matter (PM) and nitrogen
oxides (NOx) contained in the exhaust gas from the engine 7.
[0096] The target revolution speed computing unit 11a reads the
engine revolution speed Nea stored in the storage device 11f, sets
the retrieved speed as the target revolution speed for the engine
7, and outputs the set value to the engine controller 21. The
engine controller 21 computes the deviation between the target
revolution speed and the actual revolution speed of the engine 7
detected by the revolution sensor 23, computes a target fuel
injection amount corresponding to the computed deviation, and
outputs a corresponding control signal to the electronic governor
7a, whereby the engine 7 is controlled to maintain its target
revolution speed.
[0097] Although not shown, the vehicle body controller 11 may
further include another target revolution speed computing unit that
receives a command signal from the engine control dial 20 and
computes the target revolution speed based on the command signal.
In this case, a mode switch may be provided to select either the
target revolution speed computed by the target revolution speed
computing unit 11a based on the command signal from the engine
control dial 20, or the target revolution speed set by the other
target revolution speed computing unit.
[0098] The pump absorption torque computing unit 11b receives
detection signals (electric signals) from the torque sensor 19 and
thereby computes the load torque of the hydraulic pump 6 (pump
absorption torque).
[0099] The target assist torque computing unit 11c includes a
high-pass filter processing unit 11c1 and a target assist torque
conversion processing unit 11c2. FIG. 6 shows the concept of
processing by the high-pass filter processing unit 11c1, and FIG. 7
shows the concept of processing by the target assist torque
conversion processing unit 11c2. In the target assist torque
computing unit 11c, the high-pass filter processing unit 11c1 first
performs a high-pass filtering process based on a predetermined
cutoff frequency regarding the load torque of the hydraulic pump 6
computed by the pump absorption torque computing unit 11b as shown
in FIG. 6. The process removes the low-frequency component lower
than the cutoff frequency from the fluctuating load torque of the
hydraulic pump 6, thereby extracting only the high-frequency
component.
[0100] Here, the low-frequency component which is lower than the
cutoff frequency for the load torque of the hydraulic pump 6 and
which is removed from that load torque by the high-pass filter
processing unit 11c1 represents a moving average over time of the
load torque of the hydraulic pump 6. In this description, this
component is called the trend component of the load torque. Then
the target assist torque conversion processing unit 11c2 computes
target assist torque for the assist electric motor 10 based on the
high-frequency component of the load torque of the hydraulic pump 6
as shown in FIG. 7.
[0101] FIG. 8 is an illustration showing the concept of processing
by the assist electric motor power running/generation computing
unit 11d. As shown in FIG. 8, the assist electric motor power
running/generation computing unit 11d computes the power
running/generation power to be ordered to the assist electric motor
10 in accordance with the power running/generation values of the
target assist torque for the assist electric motor 10 obtained by
the target assist torque conversion processing unit 11c2 of the
target assist torque computing unit 11c, and sends control signals
accordingly to the inverter 12 to perform power running/generation
control of the assist electric motor 10.
[0102] FIG. 9 is an illustration showing the whole concept of
processing by the target assist torque computing unit 11c and by
the assist electric motor power running/generation computing unit
11d.
[0103] When the load torque of the hydraulic pump 6 (pump
absorption torque) fluctuates as indicated by a solid line on the
left-hand side of FIG. 9, the assist electric motor 10 is subjected
to power running or generation as shown in the bottom right part of
FIG. 9. That is, when the load torque of the hydraulic pump 6 is
higher than the trend component of load torque providing the
reference as indicated by a broken line on the left-hand side of
FIG. 9, the assist electric motor 10 is subjected to power running
with a counter (reverse torque) applied against the increase in the
load torque of the hydraulic pump 6, thereby preventing the large
fluctuations in the load torque of the hydraulic pump 6 from
getting transmitted unmitigated to the engine 7. Conversely, when
the load torque of the hydraulic pump 6 is lower than the trend
component of load torque providing the reference as indicated by
the broken line on the left-hand side of FIG. 9, the assist
electric motor 10 is subjected to power generation. This applies
appropriate torque to the assist electric motor 10 against a sudden
drop in the load torque of the hydraulic pump 6, whereby the abrupt
fluctuations in the load torque of the hydraulic pump 6 are
prevented from getting transmitted unmitigated to the engine 7 as
is the case when the load torque of the hydraulic pump 6 is
increased. Where the fluctuations in the load torque transmitted to
the engine 7 are suppressed in this manner, the output torque of
the engine 7 is controlled to be substantially equal to the trend
component of load torque serving as the reference indicated by the
broken line on the left-hand side of FIG. 9, as plotted by a broken
line on the right-hand side of FIG. 9. That is, it may be said that
the target assist torque computing unit 11c and assist electric
motor power running/generation computing unit 11d control the
assist electric motor 10 in such a manner as to obtain the target
output torque for the engine 7 represented by the trend component
of the load torque of the hydraulic pump 6 indicated by the broken
line on the right-hand side of FIG. 9.
[0104] FIG. 10 is a diagrammatic view showing line maps of the
emissions of particulate matter (PM) and those of nitrogen oxides
(NOx) contained in the exhaust gas from the engine 7, each of the
maps representing the correlations between the revolution speed and
output torque of the engine 7. Explained below in reference to FIG.
10 are the engine revolution speed Nea and an output torque range
Tea-Teb to be stored in the storage device 11f.
[0105] In a steady state, the emissions of particulate matter (PM)
and those of nitrogen oxides (NOx) contained in the exhaust gas
fall into a high-emission region and a low-emission region in the
correlations between the engine revolution speed and the engine
output torque as shown in FIG. 10. Although the profiles and
absolute values defining these regions vary depending on the
characteristics unique to a given engine, the emissions of PM and
those of NOx are generally in a trade-off relation to each other.
When revolution speed and torque are both high entailing high
exhaust temperatures, the emissions of NOx are high and those of PM
are low. When revolution speed and torque are both low entailing
low exhaust temperatures, the emissions NOx are low and those of PM
are high. However, from the point of view of having the emissions
of PM and those of NOx added up, there exists the region in which
the total emissions are the lowest. For example, ellipses shown in
FIG. 10 represent such regions defined by the engine revolution
speed Nea and output torque range Tea-Teb.
[0106] With this embodiment, the engine revolution speed Nea is
stored in the storage device 11f. Then, the target revolution speed
computing unit 11a performs control in such a manner that the
engine revolution speed Nea is set as the target revolution speed
for the engine 7 and that the engine revolution speed is maintained
at the revolution speed Nea defining the region in which the total
emissions of PM and NOx are the lowest. With such engine revolution
speed control in effect, the target assist torque computing unit
11c performs power running/generation control of the assist
electric motor 10 so as to ease the large load fluctuations bearing
on the hydraulic pump 6 for torque fluctuation suppression control.
This allows the output torque of the engine 7 to be maintained at
values near the output torque range Tea-Teb defining the region in
which the total emissions of PM and NOx are the lowest.
[0107] According to this embodiment structured as explained above,
the engine revolution speed is controlled to be maintained at the
revolution speed Nea defining the region in which the total
emissions of PM and NOx are the lowest. This makes it possible to
reduce the emissions of PM and NOx as air pollutants contained in
the exhaust gas. Moreover, with such engine revolution speed
control in effect, if the load torque of the hydraulic pump 6 (pump
absorption torque) becomes higher or lower than the output torque
of the engine 7, the abrupt fluctuations in the absorption torque
of the hydraulic pump 6 are prevented from getting transmitted
unmitigated to the engine 7. The output torque of the engine 7 is
controlled to be maintained within a specific range, i.e., at
values near the output torque range Tea-Teb defining the region in
which the total emissions of PM and NOx are the lowest. As a
result, it is possible to minimize the emissions of PM and NOx
contained in the exhaust gas.
[0108] Also, conventionally, the exhaust gas after-treatment device
such as the DPF (diesel particular filter) and urea SCR system is
attached to an exhaust pipe between the engine 7 and a muffler, not
shown, as indicated by dashed lines in FIG. 2. The attachment
provides the process of capturing and purifying particulate matter
(PM) and nitrogen oxides (NOx).
[0109] With this embodiment, as explained above, the assist
electric motor 10 is subjected to power running control or
generation control depending on whether the high-frequency
component of the load torque of the hydraulic pump 6 is positive or
negative, the high-frequency component being the differential
torque between the load torque of the hydraulic pump 6 and the
trend component of this load torque (target output torque for the
engine), whereby the emissions of particulate matter (PM) and
nitrogen oxides (NOx) are suppressed. This in turn makes it
possible to downsize the displacement of the DPF and the tank of
the urea SCR system, or to eliminate the exhaust gas
after-treatment device depending on the situation.
[0110] Furthermore, when the assist electric motor 10 is subjected
to power running control or generation control, the load
fluctuations bearing on the engine 7 are reduced. This provides the
additional benefit of prolonging the service life of the engine 7
as well as improving the reliability of the engine 7.
Second Embodiment
[0111] The second embodiment of the present invention is explained
below in reference to FIGS. 11 through 14. This embodiment involves
performing the same torque fluctuation suppression control as that
of the first embodiment, and setting the revolution speed and
engine output torque range of the engine 7 to regions suitable for
reducing the emissions of particulate matter (PM) and nitrogen
oxides (NOx) as air pollutants contained in the exhaust gas from
the engine 7, whereby the emissions of PM and NOx are suppressed
more effectively.
[0112] FIG. 11 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by a vehicle body controller 11A as the second
embodiment of this invention.
[0113] The vehicle body controller 11A of this embodiment includes
the functions composed of a target revolution speed computing unit
11a, a pump absorption torque computing unit 11b, a target assist
torque computing unit 11c, a torque distribution correcting unit
11e, and an assist electric motor power running/generation
computing unit 11d; and a storage device 11fA.
[0114] The detailed processes performed by the target revolution
speed computing unit 11a, pump absorption torque computing unit
11b, and target assist torque computing unit 11c are the same as in
the first embodiment and thus will not be discussed further.
[0115] The storage device 11fA stores the engine revolution speed
Nea and output torque range Tea-Teb shown in FIG. 10, the speed and
range being a specific engine speed and a specific engine output
torque range suitable for reducing the emissions of particulate
matter (PM) and nitrogen oxides (NOx) contained in the exhaust gas
from the engine 7.
[0116] The torque distribution correcting unit 11e includes an
engine output torque computing unit 11e1 and a target assist torque
correcting unit 11e2. FIG. 12 shows the concept of processing by
the engine output torque computing unit 11e1, and FIG. 13 shows the
concept of processing by the target assist torque correcting unit
11e2. In the torque distribution correcting unit 11e, the engine
output torque computing unit 11e1 first computes engine output
torque by subtracting the target assist torque obtained by the
target assist torque computing unit 11c from the load torque of the
hydraulic pump 6 (pump absorption torque) acquired by the pump
absorption torque computing unit 11b as shown in FIG. 12. The
computed engine output torque is made up of values corresponding to
the trend component of load torque serving as the reference
indicated by broken lines in FIG. 9 and others. Then the target
assist torque correcting unit 11e2 reads the output torque range
Tea-Teb (shown in FIG. 10) stored in the storage device 11fA. If
the target output torque for the engine takes values deviating from
the output torque range Tea-Teb as shown in FIG. 13, the target
assist torque correcting unit 11e2 corrects the target output
torque for the engine in such a manner that the target output
torque falls within the output torque range Tea-Teb. The amount of
the deviations from the target output torque for the engine before
the correction is added to the target assist torque obtained by the
target assist torque computing unit 11c.
[0117] FIG. 14 is an illustration showing the concept of processing
by the assist electric motor power running/generation computing
unit 11d. As with the first embodiment, as shown in FIG. 14, the
assist electric motor power running/generation computing unit 11d
computes the power running/generation power to be ordered to the
assist electric motor 10 in accordance with the values of power
running/generation of the target assist torque obtained by the
torque distribution correcting unit 11e, and sends control signals
accordingly to the inverter 12 to perform power running/generation
control of the assist electric motor 10. The control amount of
assist electric motor is also corrected in keeping with the target
assist torque corrected by the torque distribution correcting unit
11e.
[0118] With this embodiment, the storage device 11fA stores the
engine revolution speed Nea and output torque range Tea-Teb shown
in FIG. 10. Then, the target revolution speed computing unit 11a
sets the engine revolution speed Nea as the target revolution speed
for the engine 7, and performs control to keep the engine
revolution speed at the revolution speed Nea defining the region in
which the total emissions of PM and NOx are the lowest. Also, with
such engine revolution speed control in effect, the target assist
torque computing unit 11c and assist electric motor power
running/generation computing unit 11d perform power
running/generation control of the assist electric motor 10 in such
a manner as to ease the large load fluctuations bearing on the
hydraulic pump 6 for torque fluctuation suppression control, as
with the first embodiment. In addition, with the second embodiment,
the torque distribution correcting unit 11e corrects target engine
output torque when the output torque of the engine 7 under torque
fluctuation suppression control deviates from the output torque
range Tea-Teb. The output torque of the engine 7 is controlled to
stay within the output torque range Tea-Teb defining the region in
which the total emissions of PM and NOx are the lowest.
[0119] With this embodiment, as explained above, a specific engine
revolution speed Nea and a specific engine output torque range
Tea-Teb are predetermined which are suitable for reducing the
emissions of particulate matter (PM) and nitrogen oxides (NOx) as
air pollutants contained in the exhaust gas from the engine 7.
While the engine revolution speed is being controlled to remain at
the specific engine revolution speed Nea as the target engine
revolution speed, the output torque of the engine 7 is controlled
within the specific engine output torque range Tea-Teb defining the
upper and the lower limits of the target output torque for the
engine 7. In this manner, the revolution speed and output torque of
the engine 7 are controlled to stay within the region in which the
total emissions of PM and NOx shown in FIG. 10 are the lowest,
whereby the emissions of PM and NOx are further suppressed.
<Variations of the Second Embodiment>
[0120] With the above-described second embodiment, the target
revolution speed and output torque range for the engine 7 are set
to the region in which the total emissions of PM and NOx are the
lowest. Alternatively, however, the target revolution speed and
output torque range for the engine 7 may be set based on factors
other than the total emissions of PM and NOx or on other additional
factors. These factors include, for example, a combination of the
emissions of PM with the fuel consumption of the engine 7, a
combination of the emissions of NOx with the fuel consumption, a
combination of the total emissions of PM and NOx with the fuel
consumption, only the emissions of PM, and only the emissions of
NOx.
[0121] Explained first is the combination of the emissions of PM
with the fuel consumption for use in setting the target revolution
speed and output torque range for the engine 7.
[0122] FIG. 15 is a diagrammatic views showing line maps of the
emissions of particulate matter (PM) contained in the exhaust gas
from the engine 7 (right-hand side map) and the fuel consumption of
the engine 7 (left-hand side map), each of the maps representing
the correlations between the revolution speed and output torque of
the engine 7. The right-hand side map of the emissions of PM in
FIG. 15 is the same as in FIG. 10 (right-hand side map). As shown
on the left-hand side in FIG. 15, the fuel consumption of the
engine 7 falls into a high fuel consumption region and a low fuel
consumption region in the correlations between the engine
revolution speed and the engine output torque. Comparing the
emissions of PM with the fuel consumption for the relations
therebetween reveals the presence of the regions in which the
emissions of PM and the fuel consumption, in combination, are the
lowest. For example, ellipses shown in FIG. 15 represent such
regions defined by an engine revolution speed Nec and an output
torque range Tee-Tef.
[0123] Thus the storage device 11fA of the vehicle body controller
11A shown in FIG. 11 is caused to store the engine revolution speed
Nec and the output torque range Tee-Tef. The target revolution
speed computing unit 11a sets the engine revolution speed Nec as
the target revolution speed for the engine 7. When the target
output torque for the engine 7 deviates from the output torque
range Tee-Tef, the target assist torque correcting unit 11e2 of the
torque distribution correcting unit 11e corrects the target output
torque for the engine in such a manner that the target output
torque stays within the output torque range Tee-Tef. The amount of
the deviations from the target output torque for the engine before
the correction is added to the target assist torque obtained by the
target assist torque computing unit 11c. This control allows the
engine revolution speed to be maintained at the revolution speed
Nec defining the region in which the emissions of PM and the fuel
consumption are the lowest, and causes the engine output torque to
stay within the output torque range Tee-Tef defining the region in
which the emissions of PM and the fuel consumption are the
lowest.
[0124] That makes it possible not only to suppress the emissions of
PM and NOx with the assist electric motor 10 under power
running/generation control but also to further reduce the emissions
of PM and lower the fuel consumption by appropriately setting the
target revolution speed and output torque range for the engine
7.
[0125] Explained below is the combination of the emissions of NOx
with the fuel consumption for use in setting the target revolution
speed and output torque range for the engine 7.
[0126] FIG. 16 is a diagrammatic view showing line maps of the
emissions of nitrogen oxides (NOx) contained in the exhaust gas
from the engine 7 (right-hand side map) and the fuel consumption of
the engine (left-hand side map), each of the maps representing the
correlations between the revolution speed and output torque of the
engine 7. The map of the emissions of NOx and the map of the fuel
consumption are the same, respectively, as in FIG. 10 (left-hand
side map) and in FIG. 15 (left-hand side map). Comparing the
emissions of NOx with the fuel consumption for the relations
therebetween reveals the presence of the regions in which the
emissions of NOx and the fuel consumption, in combination, are the
lowest. For example, ellipses shown in FIG. 16, each defined by an
engine revolution speed Ned and an output torque range Teg-Teh,
represent such regions.
[0127] Thus the storage device 11fA of the vehicle body controller
11A shown in FIG. 11 is caused to store the engine revolution speed
Ned and the output torque range Teg-Teh. The target revolution
speed computing unit 11a sets the engine revolution speed Ned as
the target revolution speed for the engine 7. When the target
output torque for the engine 7 deviates from the output torque
range Teg-Teh, the target assist torque correcting unit 11e2 of the
torque distribution correcting unit 11e corrects the target output
torque for the engine in such a manner that the target torque stays
within the output torque range Teg-Teh. The amount of the
deviations from the target output torque for the engine before the
correction is added to the target assist torque obtained by the
target assist torque computing unit 11c. This control causes the
engine revolution speed to be maintained at the revolution speed
Ned defining the region in which the emissions of NOx and the fuel
consumption are the lowest, and causes the engine output torque to
stay within the output torque range Teg-Teh defining the region in
which the emissions of NOx and the fuel consumption are the
lowest.
[0128] That makes it possible not only to suppress the emissions of
PM and NOx with the assist electric motor 10 under power
running/generation control but also to further reduce the emissions
of NOx and lower the fuel consumption by appropriately setting the
target revolution speed and output torque range for the engine
7.
[0129] Explained below is the combination of the total emissions of
PM and NOx with the fuel consumption for use in setting the target
revolution speed and output torque range for the engine 7.
[0130] FIG. 17 is a diagrammatic view showing line maps of the
emissions of particulate matter (PM) contained in the exhaust gas
from the engine 7 (center map), the emissions of nitrogen oxides
(NOx) in the exhaust gas from the engine 7 (right-hand side map),
and the fuel consumption of the engine 7 (left-hand side map), each
of the maps representing the correlations between the revolution
speed and output torque of the engine 7. The map of the emissions
of PM and the map of the emissions of NOx are the same as in FIG.
10, and the map of the fuel consumption is the same as in FIG. 15
(left-hand side map). Comparing the emissions of PM, the emissions
of MOx, and the fuel consumption for the relations therebetween
reveals the presence of the regions in which the total emissions of
PM and MOx and the fuel consumption, in combination, are the
lowest. For example, ellipses shown in FIG. 17, each defined by an
engine revolution speed Nee and an output torque range Tei-Tej,
represent such regions.
[0131] Thus the storage device 11fA of the vehicle body controller
11A shown in FIG. 11 is caused to store the engine revolution speed
Nee and the output torque range Tei-Tej. The target revolution
speed computing unit 11a sets the engine revolution speed Nee as
the target revolution speed for the engine 7. When the target
output torque for the engine 7 deviates from the output torque
range Tei-Tej, the target assist torque correcting unit 11e2 of the
torque distribution correcting unit 11e corrects the target output
torque for the engine in such a manner that the target output
torque stays within the output torque range Tei-Tej. The amount of
the deviations from the target output torque for the engine before
the correction is added to the target assist torque obtained by the
target assist torque computing unit 11c. This control causes the
engine revolution speed to be maintained at the revolution speed
Nee defining the region in which the total emissions of PM and MOx
and the fuel consumption are the lowest, and causes the engine
output torque to stay within the output torque range Tei-Tej
defining the region in which the total emissions of PM and MOx and
the fuel consumption are the lowest.
[0132] That makes it possible not only to suppress the emissions of
PM and NOx with the assist electric motor 10 under power
running/generation control but also to further reduce the emissions
of PM and NOx and/or lower the fuel consumption by appropriately
setting the target revolution speed and output torque range for the
engine 7.
[0133] Although not described in detail, in the case where the
emissions of PM alone or the emissions of NOx alone are used in
setting the target revolution speed and output torque range for the
engine 7, as in the case of the above-mentioned other factors, a
specific engine revolution speed Nef or Neg and a specific engine
output torque range Tek-Tel or Tem-Ten for minimizing the emissions
of PM or NOx may be determined and stored into the storage device
11fA, whereby the engine revolution speed and engine output torque
may be controlled.
[0134] The foregoing paragraphs have discussed variations of the
second embodiment in which the storage device 11fA of the vehicle
body controller 11A shown in FIG. 11 is caused to store a specific
revolution speed and specific output torque different from those of
the second embodiment, so that revolution speed control of the
engine and assist torque control of the electric motor are
performed. As a variation of the first embodiment, the storage
device 11f of the vehicle body controller 11 shown in FIG. 5 may be
caused to store a similar revolution speed so that control of the
engine revolution speed and assist torque control of the electric
motor may be performed accordingly.
Third Embodiment
[0135] The third embodiment of the present invention is explained
below in reference to FIG. 18. With the second embodiment and its
variations, the storage device 11fA is caused to store the engine
revolution speed and output torque range for minimizing the total
emissions of PM and NOx, the combination of the emissions of PM
with the fuel consumption, the combination of the emissions of NOx
with the fuel consumption, the combination of the total emissions
of PM and NOx with the fuel consumption, only the emissions of PM,
or only the emissions of NOx, whereby revolution speed control of
the engine and assist torque control of the electric motor are
performed. The third embodiment involves a storage device 11fB
storing engine revolution speed and output torque range settings
for minimizing any of the combined amounts above so that any of the
settings may be selected.
[0136] FIG. 18 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by a vehicle body controller 11B of the third
embodiment of the present invention.
[0137] The vehicle body controller 11B of this embodiment includes
the functions composed of a target revolution speed computing unit
11aB, a pump absorption torque computing unit 11b, a target assist
torque computing unit 11c, a torque distribution correcting unit
11eB, and an assist electric motor power running/generation 11d;
and a storage device 11fB. Also, the hydraulic shovel of this
embodiment is provided with a mode selector switch 22 for selecting
one of a first mode through a sixth mode. The first mode is one in
which the total emissions of PM and NOx are minimized; the second
mode is one in which the emissions of PM and the fuel consumption
are minimized in combination; the third mode is one in which the
emissions of NOx and the fuel consumption are minimized in
combination; the fourth mode is one in which the total emissions of
PM and NOx and the fuel consumption are minimized in combination;
the fifth mode is one in which only the emissions of PM are
minimized; and the sixth mode is one in which only the emissions of
NOx are minimized. The mode selector switch 22 is located to be
operated by manufacturing personnel or by the manager of the
working machine. A command signal from the mode selector switch 22
is input to the target revolution speed computing unit 11aB and to
a target assist torque correcting unit 11e2B of the torque
distribution correcting unit 11eB.
[0138] The storage device 11fB stores all of the above-mentioned
engine revolution speeds Nea, Nec, Ned, Nee, Nef and Neg and the
above-mentioned output torque ranges Tea-Teb, Tee-Tef, Teg-Teh,
Tei-Tej, Tek-Tel, and Tem-Ten as the engine revolution speeds and
output torque ranges for the first through the sixth modes.
[0139] The target revolution speed computing unit 11aB receives the
command signal from the mode selector switch 22, reads the engine
revolution speed Nea, Nec, Ned, Nee, Nef, or Neg corresponding to
the input signal from the storage device 11fB, sets the retrieved
engine revolution speed as the target revolution speed for the
engine 7, and outputs the set value to the engine controller
21.
[0140] The detailed processes performed by the pump absorption
torque computing unit 11b and target assist torque computing unit
11c and the detailed processes by the engine output torque
computing unit 11e1 of the torque distribution correcting unit 11eB
are the same as those in the first and the second embodiments and
thus will not be discussed further.
[0141] The target assist torque correcting unit 11e2B of the torque
distribution correcting unit 11eB receives the command signal from
the mode selector switch 22, reads the range Tea-Teb, Tee-Tef,
Teg-Teh, Tei-Tej, Tek-Tel, or Tem-Ten corresponding to the input
signal from the storage device 11fB, and sets the retrieved torque
range. As in the case shown in FIG. 13, when the target output
torque for the engine deviates from the output torque range
Tea-Teb, Tee-Tef, Teg-Teh, Tei-Tej, Tek-Tel, or Tem-Ten thus set,
the target assist torque correcting unit 11e2B corrects the engine
target output torque in such a manner that the target output torque
stays within the set output torque range. The amount of the
deviations from the target output torque for the engine before the
correction is added to the target assist torque obtained by the
target assist torque computing unit 11c.
[0142] This embodiment allows any one of the first through the
sixth modes to be selected using the mode selector switch 22. This
makes it possible to select optimum factors from among the total
emissions of PM and NOx, the combination of the emissions of PM
with the fuel consumption, the combination of the emissions of NOx
with the fuel consumption, the combination of the total emissions
of PM and NOx with the fuel consumption, only the emissions of PM,
and only the emissions of NOx in accordance with the regulations on
the work environment and working area, whereby revolution speed
control of the engine is optimally performed and assist torque
control of the electric motor is carried out in keeping with the
regulations on the work environment and working area.
[0143] With the third embodiment, the vehicle body controller 11B
including the torque distribution correcting unit 11eB as in the
second embodiment is further equipped with the mode selector switch
22 for selecting the engine revolution speed and output torque
range. Alternatively, the vehicle body controller 11 not provided
with the torque distribution correcting unit as in the first
embodiment shown in FIG. 5 may be provided with the mode selector
switch 22 for selecting an engine revolution speed. In this case,
optimum factors can also be selected in accordance with the
regulations on the work environment and working area of the
hydraulic shovel, so that revolution speed control of the engine
may be optimally performed in keeping with the regulations on the
work environment and working area while assist torque control of
the electric motor is carried out through high-pass filter
processing of the pump absorption torque.
Fourth Embodiment
[0144] The fourth embodiment of the present invention is explained
below in reference to FIGS. 19 through 21. This embodiment
represents another method for computing pump absorption torque.
[0145] FIG. 19 is a block diagram of an actuator drive control
system of the fourth embodiment. In FIG. 19, the actuator drive
control system of this embodiment does not have the torque sensor
19. Instead of the detection signal from the torque sensor 19, a
detection signal from the revolution sensor 23 is input to a
vehicle body controller 11C.
[0146] FIG. 20 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by the vehicle body controller 11C of this
embodiment.
[0147] The vehicle body controller 11C of this embodiment includes
the functions composed of a target revolution speed computing unit
11a, a pump absorption torque computing unit 11bC, a target assist
torque computing unit 11c, a torque distribution correcting unit
11e, and an assist electric motor power running/generation
computing unit 11d; and a storage device 11fA.
[0148] The detailed processes and structures of the elements of
this embodiment other than the pump absorption torque computing
unit 11bC are the same as in the first and the second embodiments
and thus will not be discussed further.
[0149] The pump absorption torque computing unit 11bC includes an
engine revolution speed deviation computing unit 11bC1 and a pump
absorption torque estimating unit 11bC2. The detection signal from
the revolution sensor 23 is input to the engine revolution speed
deviation computing unit 11bC1.
[0150] FIG. 21 is an illustration showing the concept of processing
by the engine revolution speed deviation computing unit 11bC1 and
pump absorption torque estimating unit 11bC2.
[0151] First, the engine revolution speed deviation computing unit
11bC1 computes an engine revolution speed deviation that is the
difference between the target engine revolution speed and the
actual engine revolution speed. The target engine revolution speed
is input from the target engine revolution speed computing unit
11a. The actual engine revolution speed is a detected value of the
revolution sensor 23.
[0152] The engine revolution speed deviation computed by the engine
revolution speed deviation computing unit 11bC1 is input to the
engine controller 21. The engine controller 21 computes the target
fuel injection amount in such a manner as to reduce the engine
revolution speed deviation, and outputs a control signal
corresponding to the computed amount to the electronic governor 7a
attached to the engine 7. The electronic governor 7a acting on that
control signal injects as much fuel as the target fuel injection
amount. This controls the engine to remain at the target revolution
speed and also adjusts the output torque of the engine 7.
[0153] In addition to the output torque Te of the engine 7, a
rotating body composed of the engine 7, assist electric motor 10
and hydraulic pump 6 is subject to the load torque Tp of the
hydraulic pump 6 (pump absorption torque) and to power running or
regenerative torque Tm of the assist electric motor 10 controlled
by the inverter 12, whereby the rotating body is accelerated or
decelerated. The engine 7, assist electric motor 10, and hydraulic
pump 6 constituting the rotating body share a rotary shaft. The
revolution speed .omega. of the rotating body represents the actual
engine revolution speed. This actual engine revolution speed is fed
back to the engine controller 21 as the engine revolution speed
deviation. Because the torque of the rotating body in the
accelerating direction is defined as positive in FIG. 21, the pump
absorption torque Tp is negative, and the torque Tm of the assist
electric motor 10 is positive during power running and negative
during power regeneration.
[0154] First, consider the case where the pump absorption torque Tp
and the power running or regenerative torque Tm of the assist
electric motor 10 are 0. When the rotating body is approximated by
inertia J, the speed .omega. of the rotating body when the engine
torque Te is applied is expressed as .omega.=(1/Js).times.Te, where
"s" represents differential. Conversely, an estimate value Te' of
the applied engine torque Te can be expressed as
Te'=Js.times..omega.based on the speed of the rotating body. The
estimate value Te' thus becomes close to the actual engine torque
Te.
[0155] Where Tp and Tm are not 0, the speed .omega. is affected
thereby. It follows that Te' becomes a value including Tp and Tm
resulting in a divergence from Te. That is, Tp and Tm represent the
difference between the actual engine torque Te and the engine
torque Te' estimated from the speed. When these relations are put
together with respect to the pump absorption torque, the pump
absorption torque can be expressed as Tp'=Js.times..omega.-Te-Tm.
It should be noted that differential is approximated by the
difference or by a difference with a low-pass filter in
consideration of noise and other factors.
[0156] Here, the engine torque Te is obtained as follows. The
engine controller 21 adjusts the output torque of the engine 7 by
computing the target fuel injection amount for the engine 7 and by
causing the electronic governor 7a to increase or decrease the fuel
injection amount accordingly. The fuel injection amount is
substantially proportional to output torque. Thus the engine torque
Te is obtained from the target fuel injection amount computed by
the engine controller 21. Also, the power running or regenerative
torque Tm of the assist electric motor 10 is computed by the
vehicle body controller 11C in control of the inverter 12. The
speed .omega. of the rotating body is equal to the actual engine
revolution speed and is constituted by the value detected by the
revolution sensor 23. The inertia J of the rotating body is a known
value.
[0157] The pump absorption torque estimating unit 11bC2 obtains the
engine torque Te from the target fuel injection amount computed by
the engine controller 21, and estimates the pump absorption torque
Tp' by computing Tp'=Js.times..omega.-Te-Tm using the power running
or regenerative torque Tm of the assist electric motor 10 computed
internally by the vehicle body controller 11C, the actual engine
revolution speed .omega. as the detected value of the revolution
sensor 23, and the inertia J of the rotating body as a known
value.
[0158] With this embodiment, the pump absorption torque is computed
using an existing revolution sensor in place of the torque sensor,
so that the system can be configured inexpensively.
Fifth Embodiment
[0159] The fifth embodiment of the present invention is explained
below in reference to FIGS. 22 through 24. This embodiment
represents yet another method for computing pump absorption
torque.
[0160] FIG. 22 is a block diagram of an actuator drive control
system as the fifth embodiment. In FIG. 22, the actuator drive
control system of this embodiment includes a shuttle valve block 25
and a pressure sensor 26 in place of the torque sensor 19, with a
detection signal of the pressure sensor 26 input to a vehicle body
controller 11D.
[0161] FIG. 23 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by the vehicle body controller 11D of this
embodiment.
[0162] The vehicle body controller 11D of this embodiment includes
the functions composed of a target revolution speed computing unit
11a, a pump absorption torque predicting unit 11bD, a target assist
torque computing unit 11c, a torque distribution correcting unit
11e, and an assist electric motor power running/generation
computing unit 11d; and a storage device 11fA.
[0163] The detailed processes and structures of the elements of
this embodiment other than the pump absorption torque predicting
unit 11bD are the same as in the first and the second embodiments
and thus will not be discussed further.
[0164] The pump absorption torque computing unit 11bD includes a
proportional differential processing unit 11bD1 and a gain
processing unit 11bD2. The detection signal of the pressure sensor
26 is input to the proportional differential processing unit
11bD1.
[0165] FIG. 24 is an illustration showing the concept of processing
by the proportional differential processing unit 11bD1 and gain
processing unit 11bD2.
[0166] The proportional differential processing unit 11bD1 corrects
an error stemming from the inertia of a driven body of the actuator
drive control system, by adding a differential component to the
output pressure (hydraulic operation signal of the highest
pressure) of the shuttle block 25 which is the detected value of
the pressure sensor 26. The gain processing unit 11bD2 obtains a
predicted value of the pump absorption torque by multiplying a
proportional differential process value of the hydraulic operation
signal by a predetermined gain K.
[0167] Where the regulator 6a acting as the control device of the
hydraulic pump 6 operates on the positive or negative control
method, an increasing amount of operation of the control lever
devices 4a and 4b or of the operating member of the control penal
device raises the delivery flow rate of the hydraulic pump 6. In
keeping with the load bearing on the driven member at this time
(load of the front device 1A or of the lower track structure 1e),
the pump absorption torque as the load torque of the hydraulic pump
6 rises. The magnitude of the load on that driven member is
affected by the inertia of the driven member. Thus when the
correction is made by adding the differential component to the
hydraulic operation signal generated by the control lever devices
4a and 4b or control pedal devices, it is possible to predict the
value substantially proportional to the pump absorption torque.
[0168] With this embodiment, the pump absorption torque is
predicted using a pressure sensor available for general-purpose use
in place of the torque sensor, so that the system can be configured
inexpensively.
Sixth Embodiment
[0169] The sixth embodiment of the present invention is explained
below in reference to FIGS. 25 through 27. This embodiment involves
utilizing the output torque of the engine in place of the load
torque bearing on the engine and performing control in such a
manner that that output torque becomes the target output torque for
the engine.
[0170] FIG. 25 is a block diagram of an actuator drive control
system of the sixth embodiment. In FIG. 25, the actuator drive
control system of this embodiment is not provided with the torque
sensor 19, and a detection signal of the revolution sensor 23, in
place of that of the torque sensor 19, is input to a vehicle body
controller 11E. Also, a signal of the target fuel injection amount
internally computed by the engine controller 21 is input therefrom
to the vehicle body controller 11E.
[0171] FIG. 26 is a function block diagram showing detailed
processes of speed control and torque fluctuation suppression
control performed by the vehicle body controller 11E of the sixth
embodiment.
[0172] The vehicle body controller 11E of this embodiment includes
the functions composed of a target revolution speed computing unit
11a, an engine torque computing unit 11g, a target assist torque
computing unit 11h, and an assist electric motor power
running/generation computing unit 11d; and a storage device
11fE.
[0173] The storage device 11fE stores an engine revolution speed
Nep and output torque Tep as a specific engine revolution speed and
specific engine output torque suitable for reducing the emissions
of particulate matter (PM) contained in the exhaust gas from the
engine 7, for example.
[0174] FIG. 27 is a diagrammatic view showing a line map of
particulate matter (PM) contained in the exhaust gas from the
engine 7, the map representing the correlations between the
revolution speed and output torque of the engine 7. As shown in
FIG. 27, the engine revolution speed Nep and output torque Tep
stored in the storage device 11fE are set to a circular region in
which the emissions of PM are the lowest.
[0175] The target revolution speed computing unit 11a reads the
engine revolution speed Nep from the storage device 11fE, sets the
retrieved speed as the target revolution speed for the engine 7,
and outputs the set value to the engine controller 21. As described
above, the engine controller 21 computes the deviation between the
target revolution speed and the actual revolution speed of the
engine 7 detected by the revolution sensor 23, computes a target
fuel injection amount corresponding to the computed deviation, and
outputs a control signal reflecting the computed amount to the
electronic governor 7a to perform control so that the revolution
speed of the engine 7 is maintained at its target revolution
speed.
[0176] The engine torque computing unit 11g receives the signal of
the target fuel injection amount computed internally by the engine
controller 21 and, based on the target fuel injection amount thus
input, computes the output torque of the engine 7.
[0177] The target assist torque computing unit 11h includes a
torque deviation computing unit 11h1 and a target assist torque
conversion processing unit 11h2. The torque deviation computing
unit 11h1 reads the engine output torque Tep from the storage
device 11fE as the target output torque for the engine 7, and
computes a torque deviation by subtracting from the target output
torque Tep the engine output torque computed by the engine torque
computing unit 11g. The target assist torque conversion processing
unit 11h2 calculates the target assist torque for the assist
electric motor 10 based on the torque deviation computed by the
torque deviation computing unit 11h1.
[0178] The assist electric motor power running/generation computing
unit 11d computes the power running/generation output to be ordered
to the assist electric motor 10 in accordance with the power
running/generation values of the target assist torque for the
assist electric motor 10 obtained by the assist torque conversion
processing unit 11h2 of the target assist torque computing unit
11h, and sends a corresponding control signal to the inverter 12 to
perform power running/generation control of the assist electric
motor 10.
[0179] With this embodiment structured as described above, a
specific engine revolution speed Nep and specific engine output
torque Tep are also predetermined which are suitable for reducing
the emissions of particulate matter (PM) as air pollutants
contained in the exhaust gas from the engine 7. Control is then
performed in such a manner that the specific engine revolution
speed Nep and specific engine output torque Tep become the target
engine revolution speed and target engine output torque,
respectively. This allows the revolution speed and output torque of
the engine 7 to be controlled to minimize the emissions of PM shown
in FIG. 27, whereby the emissions of PM can be suppressed.
[0180] With the sixth embodiment, the target revolution speed and
output torque of the engine 7 are set to the engine revolution
speed Nep and engine output torque Tep in the region in which the
emissions of PM are the lowest. Alternatively, as with the
variations of the above-described second embodiment, the engine
revolution speed and output torque may be set to the regions in
which the total emissions of PM and NOx, the combination of the
emissions of PM with the fuel consumption of the engine 7, the
combination of the emissions of NOx with the fuel consumption, the
combination of the total emissions of PM and NOx with the fuel
consumption, or the emissions of NOx are the lowest. Also, as with
the above-described third embodiment, all these engine revolution
speeds and output torque ranges may be stored into the storage
device, and the mode selector switch may be provided to select an
optimum engine revolution speed and an optimum power torque output
range from the stored settings.
<Others>
[0181] The first through the sixth embodiments described above are
not limitative of the present invention, and many other variations
and modifications of the invention are possible. For example,
although the actuators for driving the swing structure on the
vehicle body were described above as constituting the motor-driven
swing system, it is also possible to adopt a system using ordinary
hydraulic swing motors. Although a single target engine revolution
speed was shown above to be set, it is also possible to set a
plurality of target engine revolution speeds of which a suitable
one is selected for control depending on the work details, work
conditions, and user settings of the hydraulic working machine.
Although the control lever device was shown above to output the
hydraulic operation signal, it is also possible to have an electric
signal output instead. Although the electric motor was shown above
to be connected serially between the engine and the hydraulic pump,
it is also possible to connect the hydraulic pump and electric
motor in parallel with the engine via a gear mechanism. Although
the load torque of the hydraulic pump (pump absorption torque) was
shown above to be subjected to high-pass filter processing, it is
also possible to subject the pump absorption torque to low-pass
filter processing and subtract the filter-processed value (trend
component) from the pump absorption torque in order to obtain the
high-frequency component. When the trend component and
high-frequency component of the load torque of the hydraulic pump
are to be computed, it is also possible to perform feed-forward
control in combination whereby such processes as differentiation
are carried out on the computed values a number of computing cycles
earlier so as to predict future values. Furthermore, the present
invention can be applied not only to hydraulic shovels but also to
other hydraulic working machines such as wheel loaders, traveling
cranes, and bulldozers.
DESCRIPTION OF REFERENCE NUMERALS
[0182] 3a Boom cylinder [0183] 3b Arm cylinder [0184] 3c Bucket
cylinder [0185] 3e, 3f Right-hand and left-hand track motors [0186]
4a, 4b Control lever devices [0187] 5a to 5c, 5e, 5f Directional
control valves [0188] 6 Hydraulic pump [0189] 6a Regulator [0190] 7
Engine [0191] 7a Electronic governor [0192] 8 Relief valve [0193] 9
Tank [0194] 10 Assist electric motor [0195] 11 Vehicle body
controller [0196] 11a Target revolution speed computing unit [0197]
11b Pump absorption torque computing unit [0198] 11c Target assist
torque computing unit [0199] 11c1 High-pass filter processing unit
[0200] 11c2 Target assist torque conversion processing unit [0201]
11d Assist electric motor power running/generation computing unit
[0202] 11f Storage device [0203] 11A Vehicle body controller [0204]
11e Torque distribution correcting unit [0205] 11e1 Engine output
torque computing unit [0206] 11e2 Target assist torque correcting
unit [0207] 11fA Storage device [0208] 11B Vehicle body controller
[0209] 11aB Target revolution speed computing unit [0210] 11fB
Storage device [0211] 11eB Torque distribution correcting unit
[0212] 11e2B Target assist torque correcting unit [0213] 11C
Vehicle body controller [0214] 11bC Pump absorption torque
computing unit [0215] 11bC1 Engine revolution speed deviation
computing unit [0216] 11bC2 Pump absorption torque estimating unit
[0217] 11D Vehicle body controller [0218] 11bD Pump absorption
torque predicting unit [0219] 11bD1 Proportional differential
processing unit [0220] 11bD2 Gain processing unit [0221] 11E
Vehicle body controller [0222] 11fE Storage device [0223] 11g
Engine torque computing unit [0224] 11h Target assist torque
computing unit [0225] 11h1 Torque deviation computing unit [0226]
11h2 Target assist torque conversion processing unit [0227] 12, 13
Inverters [0228] 14 Chopper [0229] 15 Battery [0230] 16 Swing motor
[0231] 17, 18 Pressure sensors [0232] 19 Torque sensor [0233] 20
Engine control dial [0234] 21 Engine controller [0235] 22 Mode
selector switch [0236] 23 Revolution sensor [0237] 26 Pressure
sensor
* * * * *